Paraffin isomerization process



- ferent reactions.

Patented Feb. 15, 1949 UNITED STATES PATENT OFFICE .PARAFFINFISOMERIZATION PROCESS John LPRichmon'd,'Bartlesville, kla., :assignorto *Phillips Petroleum Company, :a corporation-10f Delaware "Application November 9, 1943; SerialNoi509j611 11 Claims.

This invention relates "to "the isomerization of I parafiln hydrocarbons. "In a specific embodiment it relates totheisomerization -of low-=boil1ng parafiinyhydrocarbonsin thepresence of liquid' hy- --dro'fiuoric acid-as theisomerization catalyst, and 1 3 in-the presencepof a low-boiling cycloparaffin as 'areaction modifier. Astill more specificem- ".bodiment relates'to the isomerization of a'paraffinhydrocairbon having at least- 5 carbon atoms "per-molecule and boiling belowabout 'i50"'F., in 1 u'drocarbon :converted,r as' when two" molecules of 1a. "pentaneare converited to -one molecule of a :butaneean'd one'molecule of a hexane. Generaliilyaithe paramnsaso produced have a :Ibranched- =chain.-structure. :Itaappears :that these reactions occur concomitantly so that under-iordinaryre- .sa'ction conditionsan'diin the absence of reaction z-modifierstit -is 'not;possib1e to convert paraffin hydrocarbons .-'without' obtaining" products result- -ing from both of thesereactions.

; I :have now found: :that" when parafiin hydro- :carbons ';3E:LC011V81"8BC1 to "'othenparaffini hydrocarbons inzthe presence :of concentrated hydrofluoric *acidxasithe conversion catalysti the. second --ofthe" above 'reaction may "be: substantially and often 1 completely suppressedzby' incorporating in the reaction mixture alow-boiling' cycloparafiin. Thus. I- can. convert ta normal paraffin such as normal penta-ne to the isomeric form, .inwthis caseIiZ-rmethyibutane, :Wlth .negfigible production :of hydrocarbons: such as butanes-and hexanes =:by.,incorporating-.inthe'reaction mixture a cyclogiparaffin qsuchras a low-boiling cyclopentane or ,cyclohexane. As catalysts I iprefer to use one ain which. the v essential l catalytic :mater-ial is @hygdr'ofiuoric acid, land-generally I- prefer to associate with the "hydrofluoric acid a'minoramount ofboron trifluorida-prferably not more than per cent by weight of the catalyst -mixture, and

generally not more 'than'about '1 by weight is sufiicient.

An object of this inventionistdisomerize' lowboiling para'fiin hydrocarbons. l

Another "objectof this invention is to isomerize to 5" per cent a low-boiling paraffin hydrocarbon infthe 'presence of'concentrated hydrofluoric acid as the.

essential isomerization catalyst without converting said paraiiin hydrocarbon to paraffinehaving' higher or lowermolecular weights.

A further-object -ofthis invention is toprovide an economical process for convertingnormal butane, normal pentane,'normal hexane, or normal' heptane to corresponding isomeric parafifin hydrocarbons.

A further object of'this' invention is to con vert normal hexane to neohexane.

.A still further object of this inventionis to ro duce *diisopropylffrom a iess' highly branched hexane. I

Other objects and advantages 'of this inven- "tion' 'will becomeapparent'toone skilled in the art from the accompanying disclosure and'discussion'.

The "catalyst employed in' the "practice of my invention is essentially hydrogen fluoride and is preferably employed in'the'liquidphase. *A more active modification of the catalyst comprises liq- :uid hydrogen fluoride associated with a minor amount of boron trifluoride which need not ex- 'ceeci'about 10 per cent by weight'ofthetotal catalyst,- and is preferably between about 0.1 and about"5 to7 per cent by weight of the total catalyst. No :nickei 'or other-catalytic=agent is re- *quired and in :many cases the reactions may be carried out at temperatures near" or only "slightly above atmospheric; preferably at a temperature .betweenabout anda-b-out 300 F. Although the catalyst can be recovered'insubstantiallyzunchanged condition at' the end of the reaction and 7 can be-xreused:many'times; there'is gener'allyassociated with :thexused catalyst a 'small amount or organic-matter. .It is well'to see'toiit that'this "organic matter does" not accumulateitto too r anwextent," and when "the T catalyst :is: reused it :is iweliuto subject at aleastaa portion :of itzito a purification treatment toa'removezrsuch, organic matter. The amount of organic matter formed can often be reduced by incorporating with the catalyst a minor amount of water, and general- 13 this amount need not exceed about 1 per cent of the catalyst mixture. When boron trifiuoride is used as a component of the catalyst it should exceed the molecular equivalent of the water present since it appears that water disappears as such and enters into a, combination with the boron trifiuoride. Even in the absence of boron trifiuoride the water disappears as such and apparently enters into a combination with the hydrogen fluoride. Such a use of water in a hydrogen fluoride-boron trifiuoride catalysts is more thoroughly disclosed and discussed in Frey application Serial No. 511,444, filed November 23, 1943. Although the reaction will take place in the vapor phase it is prefered to have both the catalyst and the reactants present in liquid phase and the pressure on the system should be such that it exceeds the total vapor pressure of the reaction mixture. The amount of catalyst present should be such that when operating in the liquid phase separate catalyst and hydrocarbon phases exist, and a ratio of catalyst to hydrocarbon phases between about 0.121 and about 3:1 should be used. The catalyst and the hydrocarbon reactants should be brought into and maintained in intimate contact during the reactionperiod. Preferably such contact is effected by a mechanical mixing which results in substantial emulsification of the two phases. Satisfactorily eflicient mixing may be secured by means of a mixing pump, by passing the mixture at a high velocity through a series of baiiies, by injecting the hydrocarbon chargeat a high velocity through a jet into a body of the reaction mixture, by recirculation of the reaction mixture in a closed cycle, or the like as can be readily effected by one skilled in the art. When the re action is carried out in a long reaction zone of restricted cross-sectional area as in a tube coil, it may be found desirable to add one or more components of the catalyst at various points along the length of the reaction zone. The reaction time should be such as to effect a substantial amount of isomerization of the paraffin charge; the reaction time will vary somewhat inversely with thetemperature and more or less directly I with the concentration of the cycloparaflin employed as a reaction modifier. Thus with higher concentrations of cycloparafiin longer reaction times may be employed, other conditions being constant, without effecting unduly large amounts of reactions other than the desired isomerization reaction. Generally a reaction time less than about two hours will be satisfactory, preferably one between about 10 and about 30 minutes. The amount of cyeloparafiin employed need not exceed about 25 per cent by weight of the total hydrocarbon charge, and I have found that at least about 5 per cent by weight should be employed in order to obtain substantial benefits from the invention. It has been found that parafiin hydrocarbons which are less reactive under the reaction conditions used than the paraffin hydrocarbon being subjected to isomerization have a somewhat similar effect in suppressing reactions other than isomerization. Thus propane can be employed to aid in the isomerization of normal pentane. However, substantially larger amounts of such less reactive parafi'in hydrocarbons are necessary than for the cyclop aflins, such as up to about 50 per cent by weight.

1 of the total hydrocarbon charge.

An understanding of various aspects of my invention may be aided by referring to the accompanying drawing and the discussion thereof. This drawing is a schematic flow diagram showing one arrangement of apparatus which may be used in the practice of one embodiment of the invention. It will be readily appreciated that this drawing is in the nature of a flow diagram and that numerous individual pieces of equipment including pumps, compressors, heat exchangers, fractionating columns, etc. will be needed in any specific application of my invention.

Referring now to the drawing, a parafiin hydrocarbon such as normal pentane is introduced through pipe [0 to isomerizer H. A suitable catalyst such as liquid concentrated hydrofluoric acid containing about 5 per cent by weight of dissolved boron trifiuoride is passed to the isomerizer through pipe I! in an amount substantially equivalent to the liquid volume of the paraffin charged through pipe 10. A cycloparaiiin such as cyclohexane is passed to isomerizer II as a reaction modifier through pipe l3 in an amount such as between about 15 and 20 per cent of the total hydrocarbon material charged through pipes i9 and I3. In isomerizer II the reaction mixture is maintained in intimate admixture at a reaction temperature such as about F. for a suitable reaction time such as about 20 minutes. A portion of the reaction mixture is then passed from isomerizer ll through pipe I 4 to separator 15 wherein a separation takes place between a lighter hydrocarbon phase and a heavier liquid hydrofluoric acid phase. If desired the temperature of the separation in separating means I5 may be substantially the same as, or appreciably lower than, the reaction temperature, the latter being eifected by coolin means not shown.

From separator [5 the catalyst phase is removed through pipe IG and at least a substantial portion thereof may be returned through pipe I! to pipe 12 and into isomerizer H. In order to maintain any impurities at a desired low value, a portion of this catalyst may be withdrawn either intermittently or continuously through pipe 20 and discharged from the system, or may be passed through pipe ill to catalyst purifier 22. In catalyst purifier 22 the impurities may be removed as by distilling a substantially pure fraction comprising hydrogen fluoride and boron trifiuoride from heavier impurities. The purified catalyst may be returned to the system through pipe 23 and the impurities may be discharged through pipe 24.

From separator l5 a hydrocarbon phase may be passed through pipe 25 to separating means 26 where it is fractionated to recover desired product fractions, recycle fractions and the like. Suitable product fractions such as isopentane may be withdrawn from the system through pipe 2'! and/or pipe 28. Any light gases which are undesired may be discharged through pipe 30. A low-boiling fraction, comprising primarily hydrogen fluoride and boron trifiuoride dissolved in the hydrocarbon phase passed through pipe 25, may be separated and returned to the system through pipe 3|; A suitable recycle stream comprising unreacted parafiins such as unreacted normal pentane can be separated and returned through pipe 32. The streampassing through pipe 32 may also comprise a cycloparaffin which is suitable for use as the reaction modifier. In some instances, however,it may be found desirable to incorporate a part'or allof the cycloparafin in 6 the efliuents from thelsomerizatlonreactlonsaw Example I a part of the product removed through :pipe 21', or 2B- A ycloparaflin 1n thisstream will-have" A steelwessel' of 365 cc. volume with blades of the Same number of e nim m a stirrer revolvingy inside stationary blades at as :3 cyclopara'ffin mmany chal'gedmtm'ough 1750 RHP. M. to provide mixing was charged pipe v ith n-hexane, methyl cyclopentane, HE and Although at present. my invention is applied W l p v Y primarily to the conversion of normal orrmo'd-t BF3 given h m emtely branched hydmearbonso more highly reacted under the conditions and with the-results branched hydrocarbons it willbeunderstoodlthat shown below.

RunNm. I i m IV 5 Wt. H Y Wt. I Wt. we. Gm per cent per cent per cent per cent n-ne anean nl 82" 100 65.7 p 78.2 08. 1 oil-7 Methylcyclopentane 0 0 18/53 21.8 8N3 382.3 HF 131- 98. 0 116" 97- 1 116 9W9 BFs" 2.7 2.0 315- 2.9'- 3. '3

Time, min I 33- l Temperature; "F l 178;, 19k 176 CO'MHOSITIOTN? OF'EFFEUEISTT"HY'D'ROGARBON; PER GENT BY W EIGH'I" Propane- 2. 54

Isobutane. 25. 16

Isopentane. 18. 37

Neohexane. 13:26"

D'iisopropyl 1. 40

2 and Simethylpentan 8. 63

n-Hexane; 11.20

Methyl cyclopentanc-.. 6. 30

Cyclohexane Q22 Heavier isomerization may also take place in the reverse Example H direction if such is desirable, as when isopentanel is converted to normal pentane, and that :my 40 In asecondseries ofrunsZ-methylpehtanewas invention applies equally well to this lsomerizaused-asthe paraffin charge stock, withnmeth'yl tion. cyclopentane-zas the modifying hydrocarbon.

Run'No V VI v11 2-Methylpentaue 65'. 100" 65 lfiijea thylcyclopentme 'lime*,rmin v j Temperature, F 1'29; 160' 1 COMPOSITION OF EFFLUENT HYDROCARBON, PER CENT BY WEIGHT I Propane. Isobutane. 'n-Butane.

Isopent'ane n-P'entemm;v -Neohexane-. Diisopropyl. 2 and methylpentane; 'u-Hexane. s- Methylcyclopentaneuflnwnu Cynlnhnxnne 1 Isoheptane. 7. n fleptane 11116118337181; .c...

invention .is' further exemplified-by various runs reportedintheiollowingexamples; In'each v Em'fnple 7 H j of these-.examplesruns whichcomprisemy In.- In. a thirci'serles ofirunsgmethylcyclopentane, vention arercontrasted withiconversion .runsln cyclohexaneand n-butanewere eacmscparately which" no cycloparaffinri's used as a, reaction added I'ton'epentane; an'd'ith'e normal pcntane modifier. subjectedtoisomerization:

Run No IX X XI X11 Wt. per- Wt. per- Wt. per- Wt. per- Gm cent Gm cent Gm cent Gm cent 76 1'00 61 35.1 e1 35 17.1 25.6 0 10. 7 14. 9 0 G 0 0 0 0 0 0 10. 8 0 0 1 0 0 0 0 i 0 49.8 74.4 116 98. 0 133 96. 9 116 96. 5 117 95. 0 2.4 2.0 4.3 3.1 4.2 3.5 6.2 5.0

Time min Temperature, F 165 169 169 196 64 2. 24 20. 43 50. 33 11. 31. 86 Neohexana 4. 56 Diisopropyl 1. 30 2- and 3-methylpentanc 11. 00 n-Fl'mmno 0. 62 Methyicyclopentane 3. 67 Cyglnhmmnn 8. 78 Heptanes and heavier 12.81 2. 50

1 n-Pentance and heavie'r.

I claim:

Example IV In a fourth series of runs 1,2-dimethylcyclopentane was added to n-heptane.

1. A process for effecting the isomerization of a. low-boiling normally liquid paraflin hydrocarbon with a minimum of conversion to paraifin hydro- Run N0 XIII XIV XV Wt. per Wt. per Wt. per Gm cent cent Gm cent n-Heptane. 81. 8 82 96. 8 68. 4 81. 4 Lz-dimethylcyclopentano 0 0 2. 7 3. 2 15. 6 18. 6 146 89. 6 116 95. 4 121 95. 6 16.9 10.4 5.6 4.6 5.5 4.4

Time, min 3 40 40 Temperature, F 122 4 COMPOSITION OF EFELUENT HYDROGARBON, PER CENT BY WEIGET Propane. 1. 34 1. 30 4. 65 Isobutane 17. 80 21. 22 9. 24 milutane. 2. 7 4. 22 2. 80 Isopentan 12- 88 16. 02 3. 50 n-P n 1. 68 5. 32 Nnnhprann DiisopropyL 43 6. 69 7. 68 2- and s-methylpentone 6- 73 7. 92 n-Hexane 6 2. 68 Isoheptane- 7. 24 9. 18 20. 21 n-Heptane 60 23. 23 29. 16 Ootanes and heavier 1. 91 5. 96 1 17. 54

1 Cyclic.

From the above examples it is evident that methylcyclopentane, cyclohexane, and 1,2-dimethylcyclopentane act as inhibitors of reactojthe'term a'cyciopentane is intended to include both cyclopentane as such and alkylderivatives thereof such as methylcyclopentane.

carbons of lower and higher molecular weights, which comprises admixing with a low-boiling parafim hydrocarbon having at least five carbon atoms per molecule a low-boiling cycloparaflin having at least five. carbon atoms in the ring in an amount between about 5 and about 25 per cent 5 by weight of the total hydrocarbons, subjecting the resulting admixture to reaction at a temperature between about 50 and about 300 F. in'the presence of and intimately admixed with a liquid 7 catalyst consisting of hydrofluoric acid and be- 70 tween about 0.1 and 10 per cent by weight of boron trifluoride, with a ratio of catalyst to hydrocarbon phases between about 0.1:1 and about 3: i, for a reaction time not exceeding about two hours to isomerize said low-boiling parafiin 7 hydrocarbon, and recovering from effluents ofsaid reaction a hydrocarbon fraction containing an isomeric parafiln so produced.

2. A process for converting normal pentane to an isopentane with a minimum of conversion to other paraffin hydrocarbons, which comprises admixing with normal pentane a low-boiling cycloparafiin having at least five carbon atoms in the ring in an amount between about and about 25 per cent by weight of the total hydrocarbons, subjecting the resulting admixture to reaction at a temperature between about 50 and about 300 F. in the presence of and intimately admixed with a liquid catalyst consisting of hydrofluoric acid and between about 0.1 and per cent by weight of boron trifluoride, with a ratio of catalyst to hydrocarbon phases between about 0.111 and about 3:1, for a reaction time not exceeding about two hours to isomerize said normal pentane, and recovering from effluents of said reaction a hydrocarbon fraction containing an isopentane so producecl.

3. A process for converting normal hexane to an isohexane with a minimum of conversion to other paraffin hydrocarbons, which comprises admixing with normal hexane a low-boiling cycloparaffin having at least five carbon atoms in the ring in an amount between about 5 and about 25 per cent by weight of the total hydrocarbons, subjecting the resulting admixture to reaction, at a temperature between about 50 and about 300 F. in the presence of and intimately admixed with a liquid catalyst consisting of hydrofluoric acid and between about 0.1 and 10 per cent by weight of boron trifluoride, with a ratio of catalyst to hydrocarbon phases between about 0.1:1 and about 3:1, for a reaction time not exceeding about two hours to isomerize said normal hexane, and recovering from effluents of said reaction a hydrocarbon fraction containing an isohexane so produced.

4. A process for converting normal heptane to an isoheptane with a minimum of conversion to other paraffin hydrocarbons, which comprises admixing with normal heptane a low-boiling cycloparafiin having at least five carbon atoms in the ring in an amount between about 5 and about 25 per cent by weight of the total hydrocarbons, subjecting the resulting admixture to reaction at a temperature between about 50 and about 300 F. in the presence of and intimately admixed with a liquid catalyst consisting of hydrofluoric acid and between about 0.1 and 10 per cent by weight of boron trifluoride, with a ratio of catalyst to hydrocarbon phases between about 0.1:1 and about 3: 1, for a reaction time not exceeding about two hours to isomerize said normal heptane, and recovering from eflluents of said reaction a hydrocarbon fraction containing an isoheptane so produced.

5. A process for effecting the isomerization of a low-boiling paraifin hydrocarbon with a minimum of conversion to paraflin hydrocarbons having lower and higher molecular weights, which comprises admixing with a low-boiling isomerizable paraffin hydrocarbon a low-boiling cycloparaffin having at least five carbon atoms in the ring in an amount of at least 5 per cent and not greater than about 25 per cent by weight of the total hydrocarbons, subjecting the resulting admixture to reaction conditions such as to isomerize a substantial proportion of said parafiin hydrocarbon in the presence of an intimately admixed with an isomerization catalyst consisting of hydrofluoric acid and between about 0.1 and 10 per cent by weight of boron trifluoride, said reaction conditions in-' 1o present as separate liquid phases, with a ratio of catalyst to hydrocarbon phases between about 0.121 and about 3: 1, and recovering from efiluents of said reaction a hydrocarbon fraction comprising an isomeric paraflin so produced.

6. The process of claim 2 in which said lowboiling cycloparaifin is a cyclopentane.

7. The process of claim 3 in which said lowboiling cycloparafiin is methylcyclopentane.

8. The process of claim 4 in which said lowboiling cycloparaffin is methylcyclohexane.

9. A process for effecting the isomerization of a low-boiling parafin hydrocarbon with a minimum of conversion to paraffin hydrocarbons having lower and higher molecular weights, which comprises admixing with a low-boiling isomerizable paraffin hydrocarbon a low-boiling cycloparaflin having at least five carbon atoms in the ring in an amount not greater than about 25 per cent by weight of the total hydrocarbons,'subjecting the resulting admixture to reaction conditions such as to isomerize a substantial proportion of said paraffin hydrocarbon in the presence of and intimately admixed with an isomerization catalyst selected from the class consisting of a catalyst consisting of hydrofluoric acid and a catalyst consisting of hydrofluoric acid and between about 0.1 and 10 per cent by weight of boron trifluoride, with a ratio of catalyst to hydrocarbon phases between about 01:1 and about 3:1, and recovering from efliuents of said reaction a hydrocarbon fraction comprising an isomeric paraffin so produced.

10. An improved process for isomerizing a parafiin hydrocarbon having at least five carbon atoms per molecule, which comprises admixing with said parafiin hydrocarbon a minor amount of a normally liquid cycloparaffin hydrocarbon, subjecting the resulting admixture to reaction under isomerization conditions in the presence of a liquid catalyst consisting of hydrofluoric acid and boron trifluoride, the boron trifluoride being present in the catalyst in minor amount, and recovering from efiluents of said reaction a hydrocarbon fraction containing an isomer of said paraflin hydrocarbon so produced.

11. The process of claim 9 wherein said isomerization catalyst consists of liquid hydrofluoric acid.

JOHN L. RICHMOND.

REFERENCES CITED The following references are of record in the file of this patent:

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